The present application generally pertains to internal combustion engines and more particularly to an internal combustion engine including pre-chamber ignition.
Various pre-chamber ignition systems have been experimented with in an effort to reduce engine emissions while simultaneously increasing fuel efficiency. Such traditional systems are discussed in E. Toulson, H. Schock and W. Attard, “A Review of Pre-Chamber Initiated Jet Ignition Combustion Systems,” SAE Technical Paper, 2010-01-2263 (Oct. 25, 2010). Further examples of conventional pre-chamber engines are U.S. Patent Publication No. 2012/0103302 entitled “Turbulent Jet Ignition Pre-Chamber Combustion System for Spark Ignition Engine” which published to Attard on May 3, 2012, U.S. Pat. No. 7,107,964 entitled “Control of Auto-Ignition Timing for Homogenous Combustion Jet Ignition Engines” which issued to Kojic et al. on Sep. 19, 2006, and U.S. Pat. No. 6,953,020 entitled “Control of Auto-Ignition Timing for Combustion in Piston Engines by PreChamber Compression Ignition” which issued to Kojic et al. on Oct. 11, 2005; all of which are incorporated by reference herein. It is noteworthy, however, that the Kojic pre-chamber piston is disadvantageously intended to solely compress the pre-chamber mixture to cause auto-ignition without a spark plug or the like. Differently, the Attard device only has fuel injected into the pre-chamber and the fuel-air mixture from the combustion chamber backfeeds into the pre-chamber thereby disadvantageously causing an uncontrolled fuel and air ratio within the pre-chamber. Therefore, neither of the traditional Kojic nor Attard devices precisely control the pre-chamber fuel and air mixture nor do they precisely control the pressure within the pre-chamber. Accordingly, conventional pre-chamber ignition devices make it difficult to ignite lean fuel-air mixtures, especially at lower temperatures and in cases where high exhaust gas residuals are used to maintain low main chamber temperatures.
In accordance with the present invention, an internal combustion engine includes a pre-chamber. In another aspect, pressure within a pre-chamber is equal to or greater than pressure within a main combustion chamber at least prior to ignition in the main combustion chamber. A further aspect provides a supplemental piston creating pressure and supplying a fuel-air mixture into a pre-chamber, and a spark or glow plug has an end located within the pre-chamber for ignition of the mixture therein. In yet another aspect, internal combustion engine control software automatically controls pressure within a turbulent jet ignition pre-chamber, controls a valve-actuator to admit a fuel-air charge into the pre-chamber, causes an igniter to initiate combustion in the pressurized pre-chamber, receives a signal corresponding to pressure in the pre-chamber, and receives a signal corresponding to such pressure in a main combustion chamber of an engine block. This also permits the rate of combustion to be controlled in the primary chamber regardless of the air-fuel ratio or the diluent fraction in the main chamber. Another aspect employs a pre-chamber purge pump with separate air and fuel injection. Moreover, an additional aspect separately supplies unmixed air and fuel into a turbulent jet ignition pre-chamber through a dual-mode, single injector unit. A method of operating an internal combustion engine in an automotive vehicle is also provided.
The internal combustion engine of the present invention is advantageous over traditional devices. For example, the present device and method precisely control a pre-chamber prior to the end of compression, fuel and air mixture while also precisely controlling and causing the pre-chamber pressure to be the same as or greater than that of the main combustion chamber during at least one operating condition. This reduces if not entirely prevents backfeeding from the main chamber to the pre-chamber. The present engine also provides significant pre-chamber purging with fresh air alone, during an intake stroke of the main driving piston and during the compression process depending on operating conditions. This pre-chamber purge also lowers the overall cycle average pre-chamber wall temperature, thereby reducing heat transfer losses over prior pre-chamber ignition attempts. Furthermore, the present device is expected to significantly improve combustion of a lean fuel-air mixture or one that is heavily diluted with exhaust gas recirculation, in the main combustion chamber, even at lower operating temperatures, which should greatly reduce undesirable NOx emissions while also significantly increasing fuel efficiency. It is noteworthy that the dual-mode, single injector unit is considerably easier to package in a smaller space within a production automotive vehicle engine as compared to prior systems and even compared to the other embodiments disclosed in the present application. Additional advantages and features of the present invention will become apparent when considering the following description and appended claims as well as the accompanying drawings.